2 and half year old, highchair or normal seat?

Im getting married next May and there will be 8 small children there. One child will be 3 and a half so im going to have her on a normal seat(even though she is really naughty and will run riot) The other children range from 1 year old to 2 and a half. Should i put the 2 and a half year olds in highchairs to keep them from running around or are they too old. (Booster seats are not an option)